Desulfurization of high sulfur fluid coke particles



United States Patent bEsULFURIzATIoN OF HIGH SULFUR FLUID COKE PARTICLESJohn J. Owen, Baton Rouge, La., and John Fedirko,

Elizabeth, N. J., assignors to Esso Research and Engineering Company, acorporation of Delaware N0 Drawing. Application July 7, 1954 Serial No.441,951

2 Claims. (Cl. 202-31) basically of a reaction vessel or coker and aheater or burner vessel. In a typical operation the heavy oil to beprocessed is injected into the reaction vessel containing a denseturbulent fluidized bed of hot inert solid particles, preferably cokeparticles. Uniform temperature exists in the coking bed. Uniform mixingin the bed resultsin virtually isothermal conditions and effects almostinstantaneous distribution of the feed stock. In the reaction zone thefeed stock is partially vaporized and partially cracked. Productvaporsare removed from the coking vessel and sent to a fractionator for therecovery of gas and light distillates therefrom. Any heavy bottoms isusually returned to the coking vessel. The coke produced in the processremains in the bed coated on the solid particles. Stripping steam isinjected into the stripper to remove oil from the coke particles priorto the passage of the coke to the burner.

i The heat for carrying out the endothermic coking reaction is generatedin the'burner vessel. A stream of coke is transferred from the reactorto the burner vessel employing'a standpipe'and riser system; air beingsupplied to the riser for conveying the solids to the burner.

Suflicient coke or carbonaceous matter is burned in the burning vesselto bring the solids therein up to a temperature suflicient to maintainthe system in'heat balance. The burner solids are maintained at a highertemperature than'the solids in the reactor. About 5% of coke, based onthe feed, is burned for this purpose. This amounts to approximately 15%to of the coke made in the process. The unburned portion of the cokerepresents thenet coke formed in the process and is withdrawn.

Heavy hydrocarbon oil feeds suitable for the coking process are heavy orreduced crudes, vacuum bottoms,

pitch, asphalt, other heavy hydrocarbon residua or mixtures thereof.Typically, such feeds can have an initial boiling point of about 700 R,an A. P. I. gravity of about 0 to 20, e. g., 1.9, and a'Conradson carbonresidue content of about 5 to 40 Weight percent. (As to Conradson carbonresidue see ASTM Test D180-52.)

It is preferred to operate with solids having an average particle sizeranging between 100 and 1000 microns in diameter with a preferredaverageparticle size range be:

tween 150 and 400 microns. Product coke has an average Preferably notmore than 5%v size of 250-450 microns. has a particle size below aboutmicrons, since small particles tend to agglomerate or areswept out ofthe system with the gases. P

The method of fluid solids circulation described above is well known inthe prior art. Solids handling technique is described broadly in PackiePatent 2,589,124, issued March 11, 1952.

Fluid coking has its greatest utility in upgrading the quality of lowgrade petroleum vacuum residua and pitches from highly asphaltic andsour crudes. 'Such residua frequently contain high concentrations ofsulfur, e. g., 3 wt. percent or more, and the coke product produced fromthese high sulfur feeds are also high in sulfur content. In general thesulfur content of the coke product from the fluid coking process isabout 2 times the sulfur content of the residuum feed from which it isproduced. The sulfur content of coke from sour residue may range from 5%to 8% sulfur or more. The high sulfur content of the coke product posesa major problem in its eflicient utilization. For most non-fuel orpremium fuel uses a low sulfur content coke, below about 3 wt. percentsulfur is required. For example, low sulfur content coke is desired forthe manufacture of phosphorus, for the production of calcium carbide,for lime burning in the manufacture of soda ash or other alkalis, forvarious metallurgical application, for the production of electrodecarbon for various electrochemical applications such as the manufactureof aluminum and the like.

The conventional methods of removing sulfur from cok from ordinarysources with gaseous reagents have in general not been too satisfactory.The results are even poorer when these procedures are applied to fluidcoke. Delayed coke is more porous than fluid coke and the intersticesare more connected and larger than in fluid coke. A treating gasconsequently has relatively -easy access to the sulfur. Fluid coke, onthe other hand, is laminar in structure and may comprise some 30 tosuperposed layers of coke. Thus it is diflicult for a reagent topenetrate more than a few outer layers. These difficulties indesulfurizing fluid coke are further aggravated by the higher thannormal sulfur content of this coke derived from high sulfur petroleumfeeds.

The invention provides an improved process for desulfurizing andactivating high sulfur containing fluid coke particles-with a gaseousreagent. The process comprises treating the product coke particles witha hydrogen-containing gas at controlled, elevated temperatures andpressures whereby the sulfur content is reduced to below 3 wt. percent.

The conditions, as will be elaborated below, have been found to beimportant, as those outside the ranges stated give vastly inferiorresults.

Thus the temperature utilized is in the range of from 1100 F. to 1800F., preferably 1300" F. to 1500 F.

The pressure utilized is in the range of 30 to 300 p. s. i. g. andpreferably 50 to 250 p. s. i. g.

The time interval utilized depends on the temperature and pressure butis in the rangeof 20 minutes to 5 hours and preferably 30 to 90 minutes.

The partial pressure of hydrogen utilized is in the range of 25 to 250p. s. i. g. and preferably 50 to p. s. i. g. with 1500 to 6000v./v./hr., preferably in the range of 2500 to 5000 v./v./hr. Thehydrogen containing gas can be obtained from the gas produced in thepoker after removal ofmost of the hydrocarbons formed in the cokingoperation. Other sources of hydrogen include the pure gas or the tailgas from a hydroformer. Steam can be employed as a diluent. The hydrogencontaining gas is preferably treated in the conventional manner toremove hydrogen sulfide and other sulfur containing compounds beforeuse. The high partial pressure and concentration of hydrogen results inthe stripping of hydrogen sulfide as formed.

The treatment of this invention can be carried out in a-fluidized orbatch manner.

It is to be understood that where the term high percentage of sulfur isutilized herein it connotes more than about 4 and in cases of high.sulfur crudes more than about 7 weight percent total sulfur.

This invention will be better understood by reference tothe followingexample of its use assummarized in the following table:

EXAMPLE I Desulfuriz tian of petroleum fluid Cake with yd and othergases at 75 p. s. i. g.

Treated Product Time of Temp. of

Gas Treat, Treat,F. Wt. Wt.

min. Percent Percent Yield Sulfur of Coke in Coke These data demonstratethe marked superiority of hydrogen over other gaseous reagents for thepurpose of this invention in terms of sulfur reduction and yield. Theimprovement in sulfur removal for 1300" F. as compared to 1000 F. isalso significant.

EXAMPLE II The following data for treating petroleum fluid coke withhydrogen at atmospheric pressure indicate the necessity for treating atsuperatmospheric pressures.

Time of Wt. Per- Gas Treat, Temp. of cent Sulfur min. Treat, F. inTreated Ooke These data show that there is practically no improvement insulfur content in the absence of superatmospheric pressures even at moreelevated temperatures.

EXAMPLE III The following data show the results of treating at 75 Thelowering of the sulfur content to below 1.7 wt. percent should beparticularly noted.

The tests were conducted in the following manner. The coke to be treatedwas supported in a stainless steel reactor on a ZOO-mesh stainless steelscreen. A similar screen was placed in the top of the reactor to prevententrainment. After purging the system with nitrogen, heating was startedwhile the treating gas was passed through the system at the desiredpressure. The time of treatment given in the examples is the time oftreatment after the reactor contents reached the desired treatingtemperature. Treating gas rates, measured by the wet test meter, were inthe range of 1.5 liters/min. (STP) for about 20 grams of coke. Aftertreating for the desired time the reactor was cooled, and the coke wasremoved for inspection and analysis.

In order to express this information more fully the following conditionsof operation of the various fluid coking components by which the fluidcoke is prepared are set forth below.

Conditions in fluid coker The hydrogen treatment can be advantageouslyconducted while the coke particles are in a fixed bed or a moving fixedbed. However, a fluid bed type operation may also be employed for thehydrogen treatment. The choice of the method of contacting the coke withhydrogen will often depend upon the type of equipment available for thisoperation.

The advantages of the process of this invention will be apparent to theskilled in the art. The sulfur content is reduced to acceptable levelsby an easily controlled economical process and satisfactory yields aremaintained.

It is to be understood that this invention is not limited to thespecific examples which have been offered merely as illustrations andthat modifications may be made without departing from the spirit of theinvention.

What is claimed is:

1. A process for desulfurizing coke particles containing a highpercentage of sulfur, said particles having been produced by contactinga heavy petroleum oil coking charge stock at a coking temperature with abody of coke particles maintained in the form of a dense turbulentfluidized bed in a coking zone, wherein the oil is converted to productvapors and carbonaceous material iscontinuously deposited on the cokeparticles, removing product vapors from the coking zone, burning aportion of coke particles removed from the coking zone in a separateheating zone to increase the temperature of said coke particles,returning a portion of the heated coke particles from the heating zoneto the coking zone and withdrawing product coke particles, whichcomprises contacting the product coke particles for a time interval offrom about 30 minutes to ,5 hours with hydrogen-containing gas in atreating zone maintained at a temperature in the range of about 1300" to1500 F. and under a pressure in the range of about 50 to 25.0 p. s. i.g., the partial pressure of the hydrogen being in the range of about 25to 250 p. s. i. g., and the amount of hydrogen introduced into saidtreating zone being in the range of about 1500 to 6000 v./v./hr.,whereby the sulfur content of the product coke particles is reduced tobelow about 3 weight percent.

2. The process according to claim 1 in which the product coke particlesto be treated have a sulfur content in the range between about 4 and 8weight percent.

References Cited in the file of this patent UNITED STATES PATENTS Odellet al. May 6, 1952 Smith et al. Nov. 9, 1954 Mattox Jan. 25, 1955 GorinSept. 13, 1955 McKinley Dec. 6, 1955 Mason Oct. 18, 1955

1. A PROCESS FOR DESULFURIZING COKE PARTICLES CONTAINING A HIGHPERCENTAGE OF SULFUR, SAID PARTICLES HAVING BEEN PRODUCED BY CONTACTINGA HEAVY PETROLEUM OIL COKING CHARGE STOCK AT A COKING TEMPERATURE WITH ABODY OF COKE PARTICLES MAINTAINED IN THE FORM OF A DENSE TURBULENTFLUIDIZED BED IN A COKING ZONE, WHEREIN THE OIL IS CONVERTED TO PRODUCTVAPORS AND CARBONACEOUS MATERIAL IS CONTINUOUSLY DEPOSITED ON THE COKEPARTICLES, REMOVING PRODUCT VAPORS FROM THE COKING ZONE, BURNING APORTION OF COKE PARTICLES REMOVED FROM THE COKING ZONE IN A SEPARATEHEATING ZONE TO INCREASE THE TEMPERATURE OF SAID COKE PARTICLES,RETURNING A PORTION OF THE HEATED COKE PARTICLES FROM THE HEATING ZONETO THE COKING ZONE AND WITHDRAWING PRODUCT COKE PARTICLES, WHICHCOMPRISES CONTACTING THE PRODUCT COKE PARTICLES FOR A TIME INTERVAL OFFROM ABOUT 30 MINUTES TO 5 HOURS WITH HYDROGEN-CONTAINING GAS IN ATREATING ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF ABOUT 1300*TO1500* F. AND UNDER A PRESSURE IN THE RANGE OF ABOUT 50 T/ 25/ P. S.I.G., THE PARTIAL PRESSURE OF THE HYDROGEN BEING IN THE RANGE OF ABOUT 25TO 250 P . S. I. G., AND THE AMOUNT OF HYDROGEN INTRODUCED INTO SAIDTREATING ZONE BEING IN THE RANGE OF ABOUT 15// TO6000 V./V./HR., WHEREBYTHE SULFUR CONTENT OF THE PRODUCT COKE PARTICLES IS REDUCED TO BE LOWABOUT 3 WEIGHT PERCENT.